In conventional Personal Video Recording (PVR) systems, such as the Sky+® system, a broadcast receiver or set-top box (STB) stores a schedule of programmes to be broadcast on different channels and at different times, and presents this schedule to the user in an interactive electronic programme guide (IEPG). The user selects desired programmes or series of programmes, which are then recorded on a local recording medium, such as a hard disc, as they are broadcast. The recorded programmes may then be viewed at a time convenient to the user, and may be stored for repeated viewing or erased automatically after they are viewed. The programmes are broadcast and stored in encrypted form, the decryption process being managed via a smart card. Some programmes may be provided on a ‘pay-per-view’ basis, so that they may only be viewed if an additional payment has been made and a specific authorisation sent to the STB. A PVR system allows the user to build a collection of desired programmes, by referring to the IEPG and selecting the programmes individually or as a series from the schedule. However, the desired programmes must be available in the schedule and must either have been noticed by the user and specifically selected for recording or be automatically recorded using a ‘series link’ feature.
In a near Video on Demand (NVOD) system, programmes are broadcast repeatedly at slightly offset times, such as every 15 minutes, on different channels. The user therefore does not need to wait very long for the desired programme to be available. NVOD systems are simple to operate, but costly in terms of bandwidth.
In one type of Video on Demand (VOD) system, a library of programmes is stored at a head-end server. Users select programmes from the library and the selected programmes are streamed or downloaded to the user's STB. Users can therefore select their desired programmes without reference to a schedule. However, the bandwidth requirements of this type of VOD are very high, because a point-to-point connection is established to each user, and the instantaneous bandwidth demands of all users must be met. Consumers can also find too many different items of programming on offer daunting and less attractive than a managed choice or recommended viewing offering.
In a push VOD (P-VOD) system, a library of programmes is downloaded automatically to the user's STB, without requiring the user to pre-select any specific programme. The user may then select which of the downloaded programmes to watch. In an Internet P-VOD system, such as described in U.S. Pat. No. 6,807,558, the library of programmes is downloaded via an Internet connection. In a broadcast P-VOD system, programmes are broadcast at intervals on hidden channels and are selectively recorded by the STB so as to construct the library. Hence, although the programmes are broadcast according to a schedule, the user does not need to be aware of the schedule and is not required to select a specific programme before it is broadcast.
The P-VOD service provider is able to use its expertise and knowledge of the relative qualities of different pieces of programming, studies of viewer behaviour and viewer research in relation to viewing preferences, and specific indications of preference made by the viewer to generate a selection of recommended programmes for any given viewer. The P-VOD supplier therefore wishes to make its preferred selection of programming, based on this expertise and knowledge, available to the viewer.
The P-VOD service provider also wishes to make a larger selection of recommended programming available to the viewer. In order to provide a user friendly and pleasing service, the programming also needs to be presented to the user in an intuitive and predictable manner. For example, the consumer may be confused if programming is made available to view but is then removed from the schedule after an unexpectedly short period of time before they have had an opportunity to view it.
There are several technical obstacles facing the P-VOD service provider in offering a service with these qualities.
Although memory costs are falling and P-VOD systems have been made possible by the comparatively large number of programmes that can be stored on a local storage device, memory resource is still finite. For example, it is possible to store at least 40 hours of standard definition video on a commercially available hard disc. However, this represents only a fraction of the programmes that users might want to watch. In addition, developments such as the implementation of High Definition (HD) programming services increases the amount of memory resource required per unit time of programming. Accordingly, it is necessary to maximise and optimise the use of the available memory resource.
Broadcast PVRs also contain a finite number of tuners, which are required to receive broadcast programming at any given time. Often, PVRs will contain one or two tuners but the number can be greater. Each additional tuner involves extra cost. During ‘live’ viewing, one tuner is necessarily used by the viewer. This will also be the case if the viewer inadvertently fails to switch off their PVR and the viewing is therefore unattended. In addition, each programme selected for recording at any given time will require dedicated use of a tuner. Tuner conflicts may therefore occur.
There are also finite bandwidth resources to transmit programming. In satellite broadcasting, it may be possible to acquire additional bandwidth at the relevant orbital position but this involves significant cost which may vary depending on supply. Other distribution platforms such as digital terrestrial television (DTT) and cable have similar considerations.